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carb set up for K&N air filter and un-baffled fuel exhaust

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geewhizz
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carb set up for K&N air filter and un-baffled fuel exhaust

Post by geewhizz on Sat 21 Feb 2015, 12:49 pm

So thanks to a kind member of the forum I now have a second set of carbs to tinker with. I plan to strip them down and set them up for my cb5 with un-baffled fuel exhaust and k&n air filter and swap them over with the current set in due course. I've never even looked at a set of carb before so it all new to me. Can anyone recommend needle sizes, shims and anything else I should be considering? I'm hoping the new set-up will not completely reduce the popping on decel as I find it rather fun and hopefully the new step-up won't stifle the bike when the baffles in for the longer journeys. 

Anyone with a experience on this??  Worth doing?
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eternally_troubled
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Re: carb set up for K&N air filter and un-baffled fuel exhaust

Post by eternally_troubled on Mon 23 Feb 2015, 12:57 pm

I can't remember who did it, but, yes, someone has done this. They even did a dyno run to (or two, I think) to check.

As I recall they didn't have to change them much, in fact I think they might have only changed the main jet and then only by one size...
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geewhizz
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Re: carb set up for K&N air filter and un-baffled fuel exhaust

Post by geewhizz on Mon 23 Feb 2015, 7:38 pm

thanks ET, i had a look around the forum, and found 

http://www.cb500club.net/t1167-my-cb500-performance-upgrades

doesn't sound like results are going to be guaranteed. was this the thread you mean?
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eternally_troubled
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Re: carb set up for K&N air filter and un-baffled fuel exhaust

Post by eternally_troubled on Tue 24 Feb 2015, 12:58 pm

Yeah, that was the thread, I think in post no. 42 there are the details of the adjusted setup.

From what alexibrow was saying, the setup was significantly better than stock, assuming you had the unbaffled exhaust and K&N air filter.  I think he suggested that it sorted out some of the bad running problems.

Here is a bit of post 42 for reference:

alexibrow wrote:

OK, so to recap:

The standard fuelling set-up for the CB500 is as follows:

- Pilot screw set 2.5 turns out
- 38 pilot jet
- 122 main jet
- One needle shim.

My bike engine is standard, except for the following modifications:

- K&N panel filter
- Pipewerx Hawk SL silencer, with baffle removed.

the fuelling on my bike is set up as follows:

- Pilot screw set 3 turns out
- 38 pilot jet (standard)
- 125 main jet (one size up)
- Two needle shims (ie one additional shim).


He also then went on to mention that his tuner suggested that the slight richness observed when the bike was on the main jet might have been from the needles and/or needle holders (emulsion tubes) being worn out.

So, given that you are going to take the carbs apart it might be worth replacing those parts as well as the other modifications above, assuming you fancy spending a little (I think they might only be available from Honda!).
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brandyhands
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Re: carb set up for K&N air filter and un-baffled fuel exhaust

Post by brandyhands on Sun 01 Mar 2015, 8:15 pm

talking about carbs,i have put a flame kit on my bike. the spark is sparking but i'm not getting enough unburnt petrol in my exhaust to ignite it....how would i turn the carb up and what effects would it have?
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eternally_troubled
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Re: carb set up for K&N air filter and un-baffled fuel exhaust

Post by eternally_troubled on Mon 02 Mar 2015, 12:28 pm

Before you go playing with the carbs then you could try it by using the choke. I assume you are talking about one of those kits where you put a spark plug in your exhaust?

If you turn the choke on (possibly you might only need to do it a little bit) then there will end up being more unburn fuel in the exahust, which might have the effect you want.

If that works then you might want to try adjusting the mixture screw in the carbs, which might have some effect, but might not.

Also - just to check - you know that those things only usually work on the overrun not all the time.

sullivj
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Re: carb set up for K&N air filter and un-baffled fuel exhaust

Post by sullivj on Mon 02 Mar 2015, 6:39 pm

Why do you want flames out the back of your CB5? Rolling Eyes

I wonder what your insurer would think about you adding a non standard petrol ignightor to your bike

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